Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Dec 2009
Prolonged recruitment manoeuvre improves lung function with less ultrastructural damage in experimental mild acute lung injury.
The effects of prolonged recruitment manoeuvre (PRM) were compared with sustained inflation (SI) in paraquat-induced mild acute lung injury (ALI) in rats. Twenty-four hours after ALI induction, rats were anesthetized and mechanically ventilated with VT=6 ml/kg and positive end-expiratory pressure (PEEP)=5 cmH(2)O for 1h. ⋯ Additionally, tumour necrosis factor-alpha, interleukin-6, interferon-gamma, and type III procollagen mRNA expressions in lung tissue and lung epithelial cell apoptosis decreased more in PRM. In conclusion, PRM improved lung function, with less damage to alveolar epithelium, resulting in reduced pulmonary injury.
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Respir Physiol Neurobiol · Dec 2009
Lung volume recruitment maneuvers and respiratory system mechanics in mechanically ventilated mice.
The study aim was to establish how recruitment maneuvers (RMs) influence lung mechanics and to determine whether RMs produce lung injury. Healthy BALB/c mice were allocated to receive positive end-expiratory pressure (PEEP) at 2 or 6 cmH(2)O and volume- (20 or 40 mL/kg) or pressure-controlled (25 cmH(2)O) RMs every 5 or 75 min for 150 min. ⋯ Large RMs resulting in peak airway opening pressures (P(ao))>30 cmH(2)O did not increase inflammatory response or affect transcutaneous oxygen saturation but significantly lowered airway resistance, tissue damping and tissue elastance; the latter changes are likely associated with the bimodal pressure-volume behavior observed in mice. PEEP increase alone and application of RMs producing peak P(ao) below 25 cmH(2)O did not prevent or reverse changes in lung mechanics; whereas frequent application of substantial RMs on top of elevated PEEP levels produced stable lung mechanics without signs of lung injury.
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Respir Physiol Neurobiol · Dec 2009
Role of cholinergic-nicotinic receptors on hypoxic chemoreflex during postnatal development in rats.
We tested the hypothesis that the function of cholinergic-nicotinic receptors on respiration is age dependent. To this end, we used whole body plethysmography to measure breathing frequency (fR), tidal volume (V(T)) and minute ventilation (V (E)) under normoxia (21% O(2)) in rats at 1, 4, 7, 12 and 21 postnatal days before and after administration of epibatidine (nicotinic agonist 5 microg/kg, i.p.). In normoxia, epibatidine increased fR and V (E) in a proportionally age-dependent manner (p for age <0.001), without affecting V(T). ⋯ In P12 rats, in vitro recordings of carotid sinus nerve activity showed that superfusion with nicotine enhanced chemosensory discharge rate in normoxia and hexamethonium reduced the discharge rate in hypoxia. We also identified the nicotinic receptor alpha7 subunit by immunohistochemistry in carotid bodies from P12 rat. These data show that the role of cholinergic-nicotinic receptor on hypoxic chemoreflex is age dependent and this effect likely implicates carotid body nicotinic receptor activation.